Alerting: Rule version history API (#99041)

* implement store method to read rule versions

* implement request handler

* declare a new endpoint

* fix fake to return correct response

* add tests

* add integration tests

* rename history to versions

* apply diff from swagger CI step

Signed-off-by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>

---------

Signed-off-by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>

pkg/services/ngalert/store/alert_rule.go

@@ -118,6 +118,36 @@ func (st DBstore) GetAlertRuleByUID(ctx context.Context, query *ngmodels.GetAler
 	return result, err
 }
 
+func (st DBstore) GetAlertRuleVersions(ctx context.Context, key ngmodels.AlertRuleKey) ([]*ngmodels.AlertRule, error) {
+	alertRules := make([]*ngmodels.AlertRule, 0)
+	err := st.SQLStore.WithDbSession(ctx, func(sess *db.Session) error {
+		rows, err := sess.Table(new(alertRuleVersion)).Where("rule_org_id = ? AND rule_uid = ?", key.OrgID, key.UID).Desc("id").Rows(new(alertRuleVersion))
+		if err != nil {
+			return err
+		}
+		// Deserialize each rule separately in case any of them contain invalid JSON.
+		for rows.Next() {
+			rule := new(alertRuleVersion)
+			err = rows.Scan(rule)
+			if err != nil {
+				st.Logger.Error("Invalid rule version found in DB store, ignoring it", "func", "GetAlertRuleVersions", "error", err)
+				continue
+			}
+			converted, err := alertRuleToModelsAlertRule(alertRuleVersionToAlertRule(*rule), st.Logger)
+			if err != nil {
+				st.Logger.Error("Invalid rule found in DB store, cannot convert, ignoring it", "func", "GetAlertRuleVersions", "error", err, "version_id", rule.ID)
+				continue
+			}
+			alertRules = append(alertRules, &converted)
+		}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return alertRules, nil
+}
+
 // GetRuleByID retrieves models.AlertRule by ID.
 // It returns models.ErrAlertRuleNotFound if no alert rule is found for the provided ID.
 func (st DBstore) GetRuleByID(ctx context.Context, query ngmodels.GetAlertRuleByIDQuery) (result *ngmodels.AlertRule, err error) {